SandboxJS has a Sandbox Escape via Prop Object Leak in New Handler

published 2026-04-03 7 mo ago modified 2026-10-26 13 d ago also EUVD-2026-19301 , GHSA-hg73-4w7g-q96w

cvss: 7.2; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits: 0; none known

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.36, a scope modification vulnerability exists in @nyariv/sandboxjs. The vulnerability allows untrusted sandboxed code to leak internal interpreter objects through the new operator, exposing sandbox scope objects in the scope hierarchy to untrusted code; an unexpected and undesired exploit. While this could allow modifying scopes inside the sandbox, code evaluation remains sandboxed and prototypes remain protected throughout the execution. This vulnerability is fixed in 0.8.36.

Patch / fix

fixed in 2 links 1

npm @nyariv/sandboxjs 0.8.36
nyariv sandboxjs 0.8.36

github.com/nyariv/SandboxJS@abc02f6 commit

CISA SSVC

Exploitation: Proof of concept is public
Automatable: yes
Technical impact: partial
Assessed: 7 mo ago (2026-04-06)

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/nyariv/SandboxJS/security/advisories/GHSA-hg73-4w7g-q96w referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	6.9	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
CNA	4.0	6.9	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD	3.1	7.2	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	@nyariv/sandboxjs	<0.8.36	0.8.36

Affected products

nyariv SandboxJS

Classification

Weakness

CWE-668 Exposure of Resource to Wrong Sphere

References

github.com /nyariv/SandboxJS/commit/abc02f657279e51a4aaad2bc8f99f3e37a01b287
web
github.com /nyariv/SandboxJS/security/advisories/GHSA-hg73-4w7g-q96w
exploit, web, mitigation, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-34217
advisory
github.com /nyariv/SandboxJS
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary